A power distribution system is an interface between a power transmission network and the electricity end-customers. Typically, the power distribution system comprises a number of primary equipment and secondary equipment. In most situations, the primary and secondary devices are connected by cables, and a few primary devices comprise a communication links to the secondary devices. The primary equipment mainly comprises the equipment subject to high voltages current, e.g., transformers, circuit breakers and capacitor banks. The secondary equipment comprises the equipment subject to low voltage current and mainly acts as a controller for interacting with the primary equipment, such as Intelligent Electronic Devices (IED) and the like.
An Intelligent Electronic Device (IED) is a microprocessor-based controller of power system equipment. The IED can receive data from sensors and power equipment and issue control commands, such as tripping circuit breakers if any voltage, current, or frequency anomalies was detected, or raising/lowering voltage levels in order to maintain the desired level. A typical IED can contain line protection functions, control functions controlling separate devices, an auto-reclose function, self monitoring function, and communication functions etc. In a distribution network, the IEDs are used to directly control connected primary devices.
An IED is the controller to those directly connected primary devices, and a regional controller for all primary devices and secondary devices within the region is referred to as a master device or master. All IEDs within the region can send the information collected from primary devices to the master device. The master device controls the overall operation process of all power devices in its region.
In a power distribution network level, a network control center can be used to control and supervise the operation status of all regions. Each region includes a master device, and all master devices have a communication link to the network control center. The master devices exchange their data with network control center through the communication link. The controllers of the power network are with different hierarchical ranks. For the time being, the main communication approach of power system applications is a “vertical” one between different application hierarchies, e.g. communication between substation automation systems (e.g., master devices) and IEDs, communication between network control center and substation automation system, communication between distribution automation system and feeder terminal units. Many standards or protocols can be used in the communication mentioned above, e.g. IEC61850, DNP 3.0, IEC60870-5-104, etc.
Along with the development of power system automation, especially for SmartGrid and distributed intelligence, distributed application becomes a requirement of the trend. For example, the distribution automation functions can be distributed into sub-level to get a higher reliability and flexibility. Moreover, the future SmartGird application will have distributed applications. These distributed applications need distributed communication among them, e.g. a “horizontal” communication link among distributed master devices of the same control hierarchy to exchange data/information. Currently, there is no standard or protocol for such a horizontal communication between master devices, and there is also no common communication platform which enables data/information exchanging among these distributed applications.
In order to facilitate the overall management of a power distribution system, the whole distribution network is divided into several distribution domains. Each distribution domain is assigned with several pieces of primary equipment and defined by electrically unambiguously connected primary equipment. Each domain may include a network management controller, which is referred to as “master device”. The master device collects operating status and other operation-related parameters from all primary and secondary devices within its domain, and reports the collected domain operating status to the control center of the whole distribution network. The master device controls all power equipment within its domain by directly issuing instructions. And the distribution network control center control all power equipment with in the network by issuing in-direct instructions via master devices of each domain.
In a conventional distribution network, various master devices in different domains are unable to communicate with each other directly. In order to exchange information, a source master device shall send information to the network control center, and the network control center then forwards the information to a target master device of another domain. The conventional communication approach is obviously complicated and inefficient. In such a communication system, the communication of all subordinate devices will be interrupted when the control center is under maintenance or mal-functioned. This will cause significant trouble for the devices within the distribution network.
In order to improve the inefficiency of current vertical communication between different domains, it is one object of the invention to propose a “horizontal” inter-master devices communication method and platform. The proposed approach makes it possible to conduct direct communication between master devices at different domains.